Experimental Study on Interface Strength Between Hardened Cement Paste-Aggregate

The interfacial transition zone (ITZ) is a weak part of concrete, which is the main reason that the mechanical properties of concrete are far lower than those of hardened cement paste and aggregate itself. In order to improve the mechanical properties of concrete ITZ, the effects of cement varieties, water-binder ratio, mineral admixtures and aggregate types on the strength of hardened cement paste-aggregate ITZ were studied by orthogonal test. A linear regression model between interfacial bonding splitting tensile strength and splitting tensile strength of hardened cement paste was proposed. The results show that the water-binder ratio has the greatest impact on the mechanical properties of ITZ, followed by aggregate. The interfacial bonding splitting tensile strength of five kinds of aggregate and cement paste is in the order of marble > coral > granite > basalt > quartzite. The optimal interface test combination is as follows: water-binder ratio 0.25, aggregate is marble, P•O52.5 cement, slag content 15%, fly ash content 20% and silica fume content 10%. The optimal cement slurry combination is: water-cement ratio 0.25, basic magnesium sulfate cement, slag content 15%, fly ash content 20% and silica fume content 10%. The linear regression model between interfacial bond splitting tensile strength and hardened cement paste splitting tensile strength is established by dividing aggregate, which is of great significance to study the law of interfacial strength.